caddytls: Add support for ZeroSSL; add Caddyfile support for issuers (#3633)

* caddytls: Add support for ZeroSSL; add Caddyfile support for issuers

Configuring issuers explicitly in a Caddyfile is not easily compatible
with existing ACME-specific parameters such as email or acme_ca which
infer the kind of issuer it creates (this is complicated now because
the ZeroSSL issuer wraps the ACME issuer)... oh well, we can revisit
that later if we need to.

New Caddyfile global option:

    {
        cert_issuer <name> ...
    }

Or, alternatively, as a tls subdirective:

    tls {
        issuer <name> ...
    }

For example, to use ZeroSSL with an API key:

    {
        cert_issuser zerossl API_KEY
    }

For now, that still uses ZeroSSL's ACME endpoint; it fetches EAB
credentials for you. You can also provide the EAB credentials directly
just like any other ACME endpoint:

    {
        cert_issuer acme {
            eab KEY_ID MAC_KEY
        }
    }

All these examples use the new global option (or tls subdirective). You
can still use traditional/existing options with ZeroSSL, since it's
just another ACME endpoint:

    {
        acme_ca  https://acme.zerossl.com/v2/DV90
        acme_eab KEY_ID MAC_KEY
    }

That's all there is to it. You just can't mix-and-match acme_* options
with cert_issuer, because it becomes confusing/ambiguous/complicated to
merge the settings.

* Fix broken test

This test was asserting buggy behavior, oops - glad this branch both
discovers and fixes the bug at the same time!

* Fix broken test (post-merge)

* Update modules/caddytls/acmeissuer.go

Fix godoc comment

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

* Add support for ZeroSSL's EAB-by-email endpoint

Also transform the ACMEIssuer into ZeroSSLIssuer implicitly if set to
the ZeroSSL endpoint without EAB (the ZeroSSLIssuer is needed to
generate EAB if not already provided); this is now possible with either
an API key or an email address.

* go.mod: Use latest certmagic, acmez, and x/net

* Wrap underlying logic rather than repeating it

Oops, duh

* Form-encode email info into request body for EAB endpoint

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

2 files changed, 4 insertions, 2 deletions

diff --git a/caddytest/integration/caddyfile_adapt/global_options.txt b/caddytest/integration/caddyfile_adapt/global_options.txt
index 7e850a3..6562824 100644
--- a/caddytest/integration/caddyfile_adapt/global_options.txt
+++ b/caddytest/integration/caddyfile_adapt/global_options.txt
@@ -56,7 +56,8 @@
 					{
 						"issuer": {
 							"module": "internal"
-						}
+						},
+						"key_type": "ed25519"
 					}
 				],
 				"on_demand": {
diff --git a/caddytest/integration/caddyfile_adapt/global_options_admin.txt b/caddytest/integration/caddyfile_adapt/global_options_admin.txt
index 14bee21..9d0fb27 100644
--- a/caddytest/integration/caddyfile_adapt/global_options_admin.txt
+++ b/caddytest/integration/caddyfile_adapt/global_options_admin.txt
@@ -64,7 +64,8 @@
 					{
 						"issuer": {
 							"module": "internal"
-						}
+						},
+						"key_type": "ed25519"
 					}
 				],
 				"on_demand": {